Application of factor and cluster analyses to determine source–receptor relationships of industrial volatile organic odor species in a dual-optical sensing system

Most odor nuisance investigations rely on either human olfactory examination or on-site sampling and analytical techniques, but these methods are often subject to spatial and temporal limitations and thus impractical for locating odor emission sources. This study developed an alternative approach with a dual-optical sensing system, a meteorological station, and the combination of factor and cluster analyses to identify and characterize emission sources of multiple air contaminants. Factor and cluster analyses were employed to establish the emission profile of multiple odorous substances from each emission source. Both receptor and source monitoring data were collected to characterize the emission sources of various odorous substances. Open-path Fourier transform infrared (OP-FTIR) as a receptor path detected concurrent trends of several organic solvents with concentrations higher than the reference odor threshold values, indicating that these compounds were potential causes of odor nuisance. Qualitative source apportionment by factor and cluster analyses suggested that these odorous substances were used as organic solvents in surface coating or painting processes. Closed-cell Fourier transform infrared (CC-FTIR) at two nearby surface-coating companies indicated that only one company's stack exhibited the same odorous substance profile found by the OP-FTIR receptor path. The major odor emission source was thus identified in this study. This study demonstrated the feasibility of using the alternative investigative framework to successfully identify emission sources from an industrial odor nuisance site. The major emission sources were identified, and future enforcement plans can be conducted to enhance odor investigation efficiency and improve overall air quality.